The present invention relates to a reciprocating compressor for compressing an actuating gas up to supper-high pressure, and in particular, relates to a two-stage reciprocating compressor being suitable for compression of hydrogen gas for use, in particular, in a fuel-cell car.
Conventionally, it is already described that a diaphragm compressor is adopted, for preventing lubricating oil from mixing into a process line, as a compressor for compressing actuating gas, in a catalogue “A Diaphragm Compressor” issued in June 1982, by TEISAN, Co. Ltd., for example. Since being able to prevent the lubricating oil from mixing into, it is proposed to adopt such a kind of the compressor as the compressor for compressing hydrogen gas to be used in the fuel-cell car.
On a while, compressors are described, which compresses actuating gas up to pressure exceeding over 300 MPa, for use in a large-scale plant of 20,000–30,000 kW, for example, in U.S. Pat. No. 3,657,973, Great Britain Patent No. 1,312,843, Japanese Patent Publication No. Sho 48-12500 (1973) (U.S. Pat. No. 3,677,107), U.S. Pat. Nos. 3,801,167, and 3,510,233. Among of those, with the compressor described in U.S. Pat. No. 3,657,973, rotating movement of a crankshaft is converted into reciprocating movement of a crosshead of a frame shape. And, a plunger moves reciprocally, while a rod is guided along with a guide cylinder, and the actuating gas is compressed up to high pressure within a compressor chamber formed at a tip portion of the plunger.
More details of such a crosshead of the frame-like structure, relating to the conventional art, are described in Great Britain Patent No. 1,312,843, and also Japanese Patent Publication No. Sho 48-12500 (1973) mentioned above. In those documents, the crosshead of the frame-like structure has an upper part, a lower part and a central part thereof, and they are connected by means of a clamping bolt, clamping them at the same time. Also, a connecting rod has the structure of being divided or separated into a cross-pin portion and a crankshaft portion. Further, details of a guide-piston in such the conventional compressor are shown in U.S. Pat. No. 3,801,167 mentioned above, and details of a rod-packing seal in U.S. Pat. No. 3,510,233 mentioned above.
With the diaphragm-type compressor described in the catalogue “Diaphragm Compressor” of TEISAN, Co. Ltd., since a large amount of the lubricating oil mixes into the process line when the diaphragm is broken, therefore it is necessary to ascertain reliability of the diaphragm. For this reason, the diaphragm must be strong and large-sized under the specification of high pressure or super-high pressure, and is inconvenient to be made compact in the size thereof.
Also, in those compressors described in U.S. Pat. No. 3,657,973, Great Britain Patent No. 1,312,843, Japanese Patent Publication No. Sho 48-12500 (1973) (U.S. Pat. No. 3,677,107), U.S. Pat. Nos. 3,801,167, and 3,510,233, each the diaphragm is complex in the shape thereof, depending on the specification of the compressor, and it increases the number of steps when assembling or disassembling the compressor. Furthermore, in those documents, a certain amount of consideration was paid on the fact that the actuating gas of the compressor leaks out therefrom, however the consideration is not yet sufficient enough, in particular, for the case where the actuating gas is a flammable one, such as hydrogen gas, for example.